Thermal storage for high load short duration cooling

ABSTRACT

A thermal management system for a directed energy weapon includes a closed loop vapor compression system through which a thermal management fluid circulates. The vapor compression system including an expansion valve and an evaporator. The directed energy weapon is arranged in thermal communication with the evaporator. The expansion valve is adjustable to control a flow of the thermal management fluid provided to the evaporator in response to a mode of operation of the directed energy weapon.

BACKGROUND

Exemplary embodiments of the present disclosure relate to the art of a thermal management system, and more specifically, to a thermal management system for removing heat from a directed energy weapon (DEW).

Vehicles, such as aircraft, are being designed with advanced weapons like laser based direct energy weapons (DEWs). DEWs (e.g., laser weapons) may require substantial cooling at the lowest possible weight for sustained operation. DEWs typically operate at low efficiency and thus, generate a large amount of heat during operation, such as when the weapon is firing. DEW operation typically consists of relatively brief operating internals, wherein relatively large “bursts” of cooling are required, interspersed with relatively long intervals in which the weapon is quiescent, and therefore, requires little or no cooling. This large thermal transient may drive the size of the thermal management system used to control the thermal loading of the DEW. Such requirements may result in a thermal management system that is significantly oversized, inefficient and heavy for normal operating (non-lasing) modes. Therefore, a fast and efficient thermal management system is desired to address the thermal load of a DEW and to protect onboard components from thermal transients.

BRIEF DESCRIPTION

According to an embodiment, a thermal management system for a directed energy weapon includes a closed loop vapor compression system through which a thermal management fluid circulates. The vapor compression system including an expansion valve and an evaporator. The directed energy weapon is arranged in thermal communication with the evaporator. The expansion valve is adjustable to control a flow of the thermal management fluid provided to the evaporator in response to a mode of operation of the directed energy weapon.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the expansion valve is in a first position when the directed energy weapon is in a charging mode and the expansion valve is in a second position when the directed energy weapon is in a firing mode.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments in the first position, the valve is substantially closed and in the second position, the valve is substantially open.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the thermal management fluid has a first flow rate when the valve is in the first position and the thermal management fluid has a second flow rate when the valve is in the second position. The second flow rate is greater than the first flow rate.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments when the valve is in the second position, the thermal management fluid provided to the evaporator is a liquid.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the closed loop vapor compression system further comprises at least one thermal storage device.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the evaporator further comprises an inlet and an outlet and the at least one thermal storage device further comprises a first thermal storage device fluidly connected to and configured to provide thermal management fluid to the inlet of the evaporator and a second thermal storage device fluidly coupled to and configured to receive thermal management fluid from the outlet of the evaporator.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the thermal management fluid received within the first thermal storage device is a liquid and the thermal management fluid received within the second thermal storage device is a vapor.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments comprising a pump in fluid communication with the at least one thermal storage device. The pump is operable to move thermal management fluid from the at least one thermal storage device to the evaporator.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the thermal management fluid is refrigerant.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the thermal management fluid is carbon dioxide.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the vapor compression cycle is sized based on an average cooling required for the directed energy weapon.

Also disclosed is a method of operating a thermal management system for a directed energy weapon includes circulating a thermal management fluid through a closed loop vapor compression system including an expansion valve and an evaporator. The evaporator is in thermal communication with the directed energy weapon. The method additionally includes adjusting a position of the expansion valve to control a flow of the thermal management fluid provided to the evaporator in response to a mode of operation of the directed energy weapon.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments adjusting the position of the expansion valve further comprises moving the expansion valve to a first position when the directed energy weapon is in a charging mode.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments comprising accumulating thermal management fluid within a first thermal storage device when the directed energy weapon is in the charging mode, wherein the thermal management fluid within the first thermal storage device is a liquid.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments adjusting the position of the expansion valve further comprises moving the expansion valve to a second position when the directed energy weapon is in a firing mode.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments comprising pumping the thermal management fluid from the first thermal storage device to the evaporator when the directed energy weapon is in the firing mode.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments comprising accumulating thermal management fluid within a second thermal storage device when the directed energy weapon is in the firing mode. The thermal management fluid within the second thermal storage device is a vapor.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the thermal management fluid is refrigerant.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments the thermal management fluid is carbon dioxide.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

The FIGURE is a schematic diagram of a thermal management system for cooling a directed energy weapon according to an embodiment.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

With reference now to the FIGURE, an example of a thermal management system 20 is illustrated. In the illustrated, non-limiting embodiment, the thermal management system 20 is operable to manage the heat generated by a directed energy weapon (DEW) 30, such as a laser for example. In an embodiment, the thermal management system 20 and DEW 30 are integrated into a vehicle, such as a land vehicle or an aircraft for example.

The thermal management system 20 has a closed loop configuration through which a thermal management fluid R is configured to circulate. In the illustrated, non-limiting embodiment, the thermal management system 20 is a vapor compression system. However, it should be understood that any suitable thermal management system 20 is within the scope of the disclosure. As shown, the thermal management system 20 includes a compressor 22, a condenser or heat rejection heat exchanger 24, an expansion device 26, and an evaporator or heat absorption heat exchanger 28 arranged to form a closed fluid loop. A thermal management fluid R, such as a refrigerant or carbon dioxide, for example, is configured to flow from the compressor 22 to the condenser 24, expansion device 26, and evaporator 28 in series. In an embodiment, a motor (not shown) is operably coupled to the compressor 22 to produce work that the compressor 22 uses to compress the thermal management fluid R. However, embodiments where the compressor 22 is driven alternatively or additionally by another mechanism, such as by a turbine for example, are also within the scope of the disclosure.

In the illustrated, non-limiting embodiment, the evaporator 28 is in thermal contact or communication with a directed energy weapon (DEW) 30, such as a laser for example. The evaporator 28 is a heat exchanger configured to cool or remove heat from the DEW 30. The evaporator 28 may be configured as any suitable type of heat exchanger, including, but not limited to, a phase change evaporator with a high heat flux load, such as a plate fin cold plate, or jet impingement cold plate for example. Accordingly, not only does the evaporator 28 receive heat from the DEW 30, but also the evaporator 28 has an inlet 32 fluidly connected to an outlet 34 of the expansion device 26 by conduit 36, and an outlet 38 fluidly connected to an inlet 40 of the compressor 22 by conduit 42.

The condenser 24 of the thermal management system 20 similarly has an inlet 44 connected to an outlet 46 of the compressor 22 by a conduit 48, and an outlet 50 connected to an inlet 52 of the expansion device 26 by a conduit 54. The skilled artisan will realize that the condenser 24 (as well as the evaporator 28) can be any type of heat exchanger that achieves the desired result of heat transfer with respect to the thermal management fluid R. For example, the condenser 24 can be crossflow heat exchanger. In the illustrated, non-limiting embodiment, the condenser 24 is a liquid-air heat exchanger. A second medium A, such as ambient air or air from another source onboard the vehicle, may be arranged in a heat exchange relationship with the thermal management fluid R at the condenser 24. In an embodiment, a fan 56 is operable to push or pull a flow of the second medium A across the condenser 22. However, it should be understood that embodiments where another mechanism or alternatively, the pressure of the medium itself, is operable to move the second medium A through the condenser 24 are also within the scope of the disclosure.

During operation of the thermal management system 40, a hot vaporized thermal management fluid R is delivered from the outlet 46 of the compressor 22 to the inlet 44 of the condenser 24 through conduit 48. At the condenser 24, the themial management fluid. R is arranged in a heat exchange relationship with a cool second medium A. Within the condenser 24, heat is transferred from the hot vapor thermal management fluid R to the cool second medium A, thereby causing the hot vapor thermal management fluid R to cool and at least partially change phase to a liquid. The hot liquid thermal management fluid R at the outlet 50 of the condenser 24 is then provided to inlet 52 of the expansion device 26 through conduit 54. Within the expansion device 26, pressure is removed from the liquid thermal management fluid R, causing at least a portion of the thermal management fluid R to change state from a higher pressure liquid to a lower pressure vapor without adding heat thereto. In the illustrated, non-limiting embodiment, the thermal management fluid R provided at the outlet 34 of the expansion device 26 is a liquid and vapor mixture. However, embodiments where the thermal management fluid R at the outlet 34 of the expansion device 26 is a liquid, as will be described in more detail below, or is a vapor, are also contemplated herein.

From the outlet 34 of the expansion device 26, the thermal management fluid R is provided to the inlet 32 of the evaporator 28. Within the evaporator 28, the two-phase thermal management fluid R is arranged in a heat exchange relationship with the DEW 30. Accordingly, heat from the DEW 30 is transferred to the thermal management fluid R within the evaporator 28 such that the substantial entirety of the thermal management fluid R at the outlet 38 of the evaporator 28 is a vapor. The vaporized thermal management fluid R is delivered from the outlet 38 of the evaporator 28 to the inlet 40 of the compressor 22 through conduit 42. Within the compressor 22, the thermal management fluid R is further heated and pressurized before being delivered to the condenser 24 to repeat the cycle. In an embodiment, the thermal management fluid R is a refrigerant. However, other suitable fluids may also be used. For example, in another embodiment, the thermal management fluid R is carbon dioxide. By using carbon dioxide, the thermal management system 20 is abled to operate at a much higher pressure, thereby reducing the total amount of vapor volume required by the system.

In the illustrated, non-limiting embodiment, at least one thermal storage device is disposed along the closed fluid loop. As shown, a first thermal storage device 60, such as a liquid reservoir for example, may be arranged between the outlet 50 of the condenser 24 and the inlet 52 of the expansion device 26. In such embodiments, a pump 62 may, but need not be arranged between the condenser 24 and the first reservoir 60, such as directly upstream from the inlet 64 of the first reservoir 60 for example. A second thermal storage device 66, such as a vapor reservoir for example, may be arranged between the outlet 38 of the evaporator 28 and the inlet 40 of the compressor 22.

The thermal management system 20 may be sized based on an average load of the DEW 30 and the cooling required for such a load. In an embodiment, the expansion device 26 is a valve that is adjustable to control the flow of the thermal management fluid R therethrough based on a mode of operation of the DEW 30. For example, during normal operation of the thermal management system 20, such as when the DEW 30 is in a first state or charging mode (not firing), the valve 26 may be in a first position selected to at least partially restrict the flow of thermal management fluid R to the evaporator 28. By limiting the flow through the valve 26, and because the flow through the compressor is greater than the flow rate through the valve 26, all or at least a portion of the liquid thermal management fluid R output from the condenser 24 will accumulate within the first reservoir 60. In such embodiments, the position of the expansion valve 26 may be selected to allow only the flow of thermal management fluid R necessary to adequately cool the DEW 30 therethrough. In some embodiments, when in DEW 30 is in the charging or recharging mode, no cooling of the DEW 30 is required, and therefore the valve 26 may be fully closed such that no flow is provided to the evaporator 28.

During operation of the thermal management system 20 in a high cooling mode, such as when the DEW 30 is in a second state or firing mode for example, the valve 26 is adjusted to a second position. The second flow rate at the valve 26 associated with the second position thereof is significantly increased relative to the first flow rate associated with the valve 26 in the first position. Accordingly, in an embodiment, the first position of the valve 26 may be considered partially or fully closed and the second position of the valve 26 may be considered fully open.

By opening or further opening the valve 26 when the DEW 30 is firing, a greater amount of thermal management fluid R is provided to the evaporator 28, thereby increasing the cooling of the DEW 30 that is performed via the evaporator 28. When the valve 26 is in the second position, pressure may not be removed from the thermal management fluid R at the expansion device 26. In such embodiments, the thermal management fluid R may remain a liquid at the outlet 34 of the expansion device 26.

In addition, in an embodiment, during operation in the high cooling mode, the excess liquid thermal management fluid R accumulated within the first reservoir 60 is combined with the circulating flow of thermal management fluid R, such as via pump 62 for example, to accommodate the increased flow rate at the valve 26. In an embodiment, all or the majority of the thermal management material R provided to the evaporator 28 is substantially liquid to increase the amount of heat that can be absorbed from the DEW 30 within the evaporator 28. As a result of the increased heat during operation of the laser, the thermal management fluid R provided at the outlet 38 of the evaporator 28 is a vapor. From the evaporator 28, the thermal management fluid R is generally provided to the compressor 22. However, because the flow rate of the thermal management fluid R at the outlet 38 of the evaporator 28 is greater than the flow rate at the inlet 40 of the compressor 22, during operation in the firing mode, the excess vapor thermal management fluid R will accumulate within the second reservoir 60. Once the thermal management system 20 transforms back to the first mode of operation, the accumulated thermal management fluid R will be drawn from the second reservoir 60.

A thermal management system 20 having a first and second thermal storage device as described herein integrates the thermal storage into the vapor cycle. As a result, additional thermal storage means can be eliminated and the thermal management system may be sized based on the average cooling load for the DEW 30, rather than the maximum cooling load.

The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.

While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims. 

What is claimed is:
 1. A thermal management system for a directed energy weapon comprising: a closed loop vapor compression system through which a thermal management fluid circulates, the vapor compression system including an expansion valve and an evaporator, the directed energy weapon being arranged in thermal communication with the evaporator; wherein the expansion valve is adjustable to control a flow of the thermal management fluid provided to the evaporator in response to a mode of operation of the directed energy weapon.
 2. The thermal management system of claim 1, wherein the expansion valve is in a first position when the directed energy weapon is in a charging mode and the expansion valve is in a second position when the directed energy weapon is in a firing mode.
 3. The thermal management system of claim 2, wherein in the first position, the valve is substantially closed and in the second position, the valve is substantially open.
 4. The thermal management system of claim 2, wherein the thermal management fluid has a first flow rate when the valve is in the first position and the thermal management fluid has a second flow rate when the valve is in the second position, the second flow rate being greater than the first flow rate.
 5. The thermal management system of claim 2, wherein when the valve is in the second position, the thermal management fluid provided to the evaporator is a liquid.
 6. The thermal management system of claim 1, wherein the closed loop vapor compression system further comprises at least one thermal storage device.
 7. The thermal management system of claim 6, wherein the evaporator further comprises an inlet and an outlet and the at least one thermal storage device further comprises a first thermal storage device fluidly connected to and configured to provide thermal management fluid to the inlet of the evaporator and a second thermal storage device fluidly coupled to and configured to receive thermal management fluid from the outlet of the evaporator.
 8. The thermal management system of claim 7, wherein the thermal management fluid received within the first thermal storage device is a liquid and the thermal management fluid received within the second thermal storage device is a vapor.
 9. The thermal management system of claim 6, further comprising a pump in fluid communication with the at least one thermal storage device, the pump being operable to move thermal management fluid from the at least one thermal storage device to the evaporator.
 10. The thermal management system of claim 1, wherein the thermal management fluid is refrigerant.
 11. The thermal management system of claim 1, wherein the thermal management fluid is carbon dioxide.
 12. The thermal management system of claim 1, wherein the vapor compression cycle is sized based on an average cooling required for the directed energy weapon.
 13. A method of operating a thermal management system for a directed energy weapon, the method comprising: circulating a thermal management fluid through a closed loop vapor compression system including an expansion valve and an evaporator, the evaporator being in thermal communication with the directed energy weapon; and adjusting a position of the expansion valve to control a flow of the thermal management fluid provided to the evaporator in response to a mode of operation of the directed energy weapon.
 14. The method of claim 13, wherein adjusting the position of the expansion valve further comprises moving the expansion valve to a first position when the directed energy weapon is in a charging mode.
 15. The method of claim 14, further comprising accumulating thermal management fluid within a first thermal storage device when the directed energy weapon is in the charging mode, wherein the thermal management fluid within the first thermal storage device is a liquid.
 16. The method of claim 15, wherein adjusting the position of the expansion valve further comprises moving the expansion valve to a second position when the directed energy weapon is in a firing mode.
 17. The method of claim 16, further comprising pumping the thermal management fluid from the first thermal storage device to the evaporator when the directed energy weapon is in the firing mode.
 18. The method of claim 16, further comprising accumulating thermal management fluid within a second thermal storage device when the directed energy weapon is in the firing mode, wherein the thermal management fluid within the second thermal storage device is a vapor.
 19. The method of claim 13, wherein the thermal management fluid is refrigerant.
 20. The method of claim 13, wherein the thermal management fluid is carbon dioxide. 